Auriga: The Charioteer

In Case You’ve Never Seen It Before..

An Old Constellation

•Gigir “The Chariot” - the name given it in ancient Sumeria between 3500 & 2500BC.•Heniochos “The Charioteer” -its classic Greek name. •Auriga “The Charioteer” -its latin name from the Romans.

Who’s the Charioteer? Take your pick!

Hephaetus Myrtilus

PoseidonErichthonius

…And What’s Up with the Goat?

•Capella, the brightest star, is old Roman for “The She-Goat.”•The Romans recognized Epsilon, Zeta & Eta Aur as “The Kids”•The Greeks only saw two Kids, Zeta & Eta•No mythological basis. Perhaps Mom & the kids are best treated as own asterism.

Constellation Facts• Abbreviation: Aur• Coords: RA 6 h Decl: +40° • Area: 657 sq. deg. (21st/88) • Brightest star: Capella (α

Aur) (0.8mag ) • Nearest star: QY Aur (20.0 ly)

Messier objects: 3• Meteor showers: Alpha Aurigids (Aug 25th- Sep 6th))Delta Aurigids (Sept-22 to Oct 23)• Bordered by

CamelopardalisPerseusTaurusGeminiLynx

Where’s it at?

Finding It: Winter Hexagon

From Cheryl Haimann’sBackyard Astronomywww.pikerpress.com(Used with permission)

Finding It From Orion

From Cheryl Haimann’sBackyard Astronomywww.pikerpress.com(Used with permission)

Finding it (cont’d)

Use top 2 stars in Big Dipper’s bowl and head west 70 degrees. You’ll run into Capella

The Pentagon, or “Five Chariots”

•Capella (mag 0.8) “She-Goat”, 6th brightest star in the sky•Mankalinan (mag 1.9) “Shoulder of the Reinholder”•Bogardus (2.62)•AlKab( Hassaleh)(2.69)•ElNath (1.6) “Butting One”, technically Beta Tauri

Capella- The “She-Goat” is Twins

•Capella a & b are both G-class giants, of around 3 solar masses each. They probably started life on the main sequence as A-class dwarfs, but are early into their red giant phase.•The two suns circle each other at a distance closer than our earth-sun distance (0.73 AU). Their combined luminosity is 150 times our sun.•Capella is circumpolar at our latitude.

The AntiCenter of our Galaxy is in Auriga

Those Wonderful Open ClustersM36,M37,M38

M38

M37

M36

AE Aurigae & the Flaming Star Nebula

AE Aur is a “runaway” star ejected from the star-forming region in Orion some 2.7 million years ago. It’s big, young, and bright, and illuminates its current area of space, producing the Flaming Star Nebula (IC 405).

Variables in Auriga•Zeta Aurigae is an eclipsing binary. Every 2.6 years, it dims ½ magnitude for 40 days.

•Beta Aurigae (Menkalinan) is an EB too, dimming 0.1 magnitude for 10 hours every 4 days.

•AE Auriga (remember the flame star?) varies between mag 5.8 & 6.1 , being young & wild (INA).

Epsilon Aurigae:“This Strange Star”• A Class F Supergiant• First noted to vary in brightness in 1821.• Observations in 1847-48, 1874-75,1901-2

showed it dimming for periods of 2 years! • Hans Ludendorff proposed in 1904 that

Epsilon Aurigae is an Eclipsing Binary with a period of 27.1 years.

• Last eclipse was 1982-84. Next predicted eclipse is 2009-11.

• How can an eclipse take two years?

How Eclipsing Binaries Work

• One companion star gets in our line of sight of the other, blocking some part the light we see.

• For this to work for Epsilon Auriga, the occluding star would have to be HUGE- 3000 AU!

• If it’s not a star, how about a disk of matter?

The Eclipsing Disk Model

• A disk of matter around the star that’s not in our line of site all of the time, but periodically gets in the way and dims the light we receive.

• There’s still a problem with this model if we look at the light curves from past eclipses…

It gets brighter in the middle of the eclipse. We need a hole- a donut?

The Current “Orbiting Donut” Model

•Two B- class stars orbit each other, and are surrounded by a big circum-stellar disk. •This young, messy system in turn shares an orbit with our F0 suoergiant primary.•In our line of sight, light can pass through the “transparent” B stars in the middle of the eclipse.

Watch for it !•First Contact August 6 2009 (est)•Midoint Aug 10 2010 (est)•Done May 15 2011 (647 Days total)

0.1

3.2 3.8

2.7

2.8-?

Resources

• American Association of Variable Star Observers: http://www.aavso.org

• Epsilon Aurigae Campaign Page: http://www.hposoft.com/Astro/PEP/EpsilonAurigae.html

• IYA 2009 Epsilon Aurigae Project: http://astronomy2009.us/citizen_science/epsilon-aurigae/

• Feb 2009 Sky & Telescope Celestial Calendar Column

That’s It!!!